Ignition system



J. B. FARR IGNITION SYSTEM May 28, 1968 Filed May 13, 1964 h VKbDOR W United States Patent 3,386,0tltl HGNETHGN SYSTEM James B. Farr, Madison Heights, Mich, assignor to Chrysler Corporation, Highland Park, Mich, a corporation of Delaware Filed May 13, 1964, Ser. No. 366393 9 @laims. (Cl. 315-239) This invention relates generally to internal combustion engines and more particularly to an ignition system for use with such an engine.

Automotive engines are being designed for greater engine efficiency and higher engine operating speeds. Engine compression ratios have been increased as a means of obtaining increased efficiency; however, such increase compression ratios and engine speeds have, in turn, created ignition operating requirements which are extremely difficult to obtain with the conventional breaker point and coil type of ignition system.

Such more demanding ignition operating requirements, even if initially satisfied by said conventional ignition systems, cause a rapid deterioration thereof so as to quickly render such an ignition system inadequate. For example, in order to attain sufficient voltage in the higher range of engine speeds and because of the shorter dwell time of the breaker points at the higher en ine speeds, the ignition coil is often exposed to the danger of 0versaturation in the range of lower engine speeds.

Further, the making and breaking of the circuit through the breaker-point contacts is accomplished by a cam actuated in timed relationship to engine operation. Accordingly, as engine speed increases the frequeny of actuation by the cam correspondingly increases. As a consequence of such increased frequency and the masses of the components involved, the condition often referred to as breaker point bounce occurs, indicating that the breaker contacts are not remaining in a stable closed condition during the dwell period during which time charging of the ignition coil is to be accomplished. Attempts to assure proper breaker contact closure during higher engine speeds as by the provision of lower rate biasing spring, urging the breaker contacts in the direction of contact closure, has proven to only aggravate the problem of contact bounce.

Also, higher ignition voltages have cause a more rapid pitting and deterioration of the breaker contacts which are inherently susceptible to oxide formation.

Various ignition systems have heretofore been proposed in an attempt to overcome the problems attendant the conventional breaker type ignition system. For example, transistors have been employed for performing the switching function for charging the coil thereby replacing the breaker contacts for that particular function; however, in such transistorized systems, the conventional breaker contacts are still employed (and actuated in the conventional manner) for causing the transistor to be come conductive and nonconductive in timed relationship to engine rotation. In such systems, increased breaker contact life has been experienced because the voltage and current carrying requirements of the contacts have been materially reduced to that value necessary for only switching the transistor.

Even though such transistorized systems have proven to be of some benefit, they are nevertheless ultimately dependent upon the mechanical breaker contacts. That is, the dwell time at higher engine speeds is still relatively short and the coil, which is charged through the transistor, is again, in many instances, insulficiently charged. Further, at high engine speeds mechanical breaker contacts still experience bounce thereby further diminishing the total time available for charging the coil. Accordingly, it can be seen that even though some advantages are 3,386,090 Patented May 28, 1968 obtained from such a mechanically switched transistorized ignition system that such systems are still .limited by much the same drawbacks or undesirable characteristics of the conventional breaker and coil ignition system.

Another variation of the above transistorized ignition system employs a contactless pulsor comprised of a magnetic pick-up or probe intersecting a second magnetic field for creating magnetic field disturbances which are employed for making an associated transistor conductive in timed relation to engine rotation. This basic arrangement has the apparent advantage of eliminating all of the undesirable characteristics of the mechanical breaker point contacts. However, other disadvantages occur from this type of circuit. For example, the output voltage of the magnetic probe is dependent upon the seed at which the magnetic field is traversed by the magnetic probe. Consequently, at low engine speeds, as, for example, during engine cranking, it is difficult to obtain an output from the magnetic pickup which is sufficient to operate the transistor.

Further, with varying ambient temperatures and consequently varying temperatures of the magnet and the pickup, varying voltages are realized. Such variations may cause the output from the magnetic pick-up to diminish to a degree which is insufficient to operate the ignition system.

Also, ignition systems must be advanced and/or retarded depending on such factors as engine speed and load. Ignition systems employing pulsors as described above, do not have the ability to properly advance and retard over the full range of engine speeds. This, it is believed, is due at least in part to the various eddy currents developed within the pick-up and the capacitive feedback in the coil associated with the magnetic pick-up. Such variations coupled with variations in ambient temperatures, as referred to above, present an ultimate ignition coil output which can not be readily predicted with a sufiicient degree of certainty to enable proper compensation.

Another type of ignition system is sometimes referred to as a capacitive energy storage ignition system. In this system a source of direct current charges a capacitor which is subsequently discharged by a transistor. Due to circuit complexities and the related high costs, such capacitive systems have not been employed to any discernible extent.

Other variations of transistorized ignition systems have been employed; however, none of these have found any appreciable degree of acceptance especially by the automotive industry.

Accordingly, it is a general object of this invention to provide a novel and improved ignition system, for use with an internal combustion engine, which is not dependout upon any mechanical switching in order to achieve timed energy discharge.

Another object of this invention is to provide an improved ignition system employing a light sensitive semiconductor device for controlling the ignition circuit.

A further object of this invention is to provide a transistorized ignition system employing a light sensitive semiconductor device and feedback means sensitive to the occurrence of a sparking event in the ignition system for causing the semi-conductor to become non-conductive.

Yet another object of this invention is to provide in a transistorized ignition system, feedback means sensitive to a sparking event for causing both a light sensitive semiconductor device and an associated transistor to become non-conductive.

Other objects and advantages of the invention will become apparent when reference is made to the following description and accompanying drawings wherein:

FIGURE 1 is a schematic wiring diagram of one em- 3 bodiment of an ignition system constructed in accordance with the teachings of this invention; and

FIGURES 2 through 7 are graphs of curves illustrating characteristics of designated portions of the ignition system as disclosed in FIGURE 1.

Referring now in greater detail to the drawings, FIG- URE 1 illustrates an embodiment of the invention as comprising a source of electrical potential 10, a silicon controlled rectifier (SCR) 12 and a PNP type transistor 14 operatively connected to a transformer or spark coil 16 having a primary winding 18 and a secondary winding 20. The secondary winding 20 as indicated may be suitably connected to the rotating arm 22 of an ignition distributor 24 having distributor segments or terminals 26 which are respectively operatively connected to the spark plugs 28, of engine 29, all of which are grounded as at 30.

An electrical conductor 32, having serially connected therein an ignition switch 34 and resistors 36 and 38, is connected to the positive terminal 40 of the source of electrical potential 10 and to the emitter electrode 42 of transistor 14. The collector electrode 44 of transistor 14 has connected thereto a conductor 46 which is also connected to terminal 48 of the ignition coil assembly 16. Conductor 46 has serially connected therein a coil or winding 50 and a resistor 52. Terminal 54 of coil assembly 16 has connected thereto a conductor 56 which leads to the ignition distributor rotor 22, while terminal 58 of the coil assembly is electrically connected to the negative terminal 60 of source 10 as by means of a conductor 62.

A movable shield or shutter mechanism, as illustrated by a disc 64 which is provided with a plurality of slits 66, is interposed between a source of light, such as lamp 68, and the photoconductive device 12. Disc 64 is rotated in timed relationship to rotor 22 as by means of suitable transmission means driven by engine 29. Slits 66 are of a size and so positioned so as to permit light emanating from source 68 to pass through one of the slits 66 (as schematically depicted by line 67) and impinge upon the SCR 12 whenever rotor 22 is generally in juxtaposition to one of the distributor segments 26.

A conductor 72 connected at one end to conductor 32, at a point intermediate resistances 36 and 38, and connected at its other end to conductor 62, has serially connected therein the SCR 12 and a resistor 74-.

A conductor 76 connected to conductor 32, as by means of conductor 72, is serially connected with a resistor 78 and conductors 80 and 82, which are in parallel relationship to each other and also connected to conductor 62. Conductor 82 has lamp 68 connected in series therewith while conductor 80 contains serially connected diodes 84, S6 and 88 which collectively function as a voltage regulator for lamp 63.

The gate electrode 20 of the SCR 312 has connected thereto a resistor 92 which is connected at its other end to conductor 72 at a point 94 intermediate the SCR 1 2 and resistor 74. Resistor 92 preferably is a combination resistor-hermistor. Also electrically connected to point 94, as by a conductor 96, is a coil or winding 98 which has its other end connected to the base electrode 109 of transistor 14.

A Zener diode 102 connected to conductors 32 and 46 in parallel relationship with transistor 14 is provided as a protection for the transistor should excessive voltages thereacross be experienced. Switch 104 may be provided so as to be closed during engine cranking thereby shunting the resistance 36 during the cranking period. Once engine operation becomes self-sustaining switch 164 would be opened thereby placing resistance 36 in circuit.

For purposes of describing the operation of the invention, let the following conditions be assumed to exist: (a) ignition switch 34 is closed; (b) shunting switch 1534- is open; (c) the associated iternal combustion engine containing spark plugs 28 is self-sustaining; (d) rotor 22 is being rotated and at the initial instant of consideration is intermediate consecutive terminals 26 and (e) the shutter mechanism or disc 64- because of its timed rotation relative to rotor 22 is at a position whereat all apertures 66 are out of alignment with light source 68 and SCR 12.

With the above assumed conditions it can be seen that with switch 34 being closed electrical source 10 biases the emitter 42 and base circuit of the transistor in a direction which causes the emitter-collector circuit to become conductive. The value of the resistance of coil winding 98 and the resistance of resistor 74 is selected so that sufi'lcient base current flows whenever the ignition switch 34 is closed so as to cause the transistor 14 to become fully conductive from emitter 42 to collector 44.

During this period, still at the assumed conditions, a substantially constant current is supplied not only to the primary windings 18 of the coil assembly 16 but also through winding 50, winding 98 in the transistor base circuit, resistor 74 and bulb 68. Coils 50 and 98 along with the associated core 166 can be considered as comprising a transformer as will become apparent in view .of the description to follow.

As disc 64 and rotor 22 are rotated from their previously assumed positions to those as illustrated in FIGURE 1, light supplied by lamp 63 is permitted to pass through an aligned slit 66 of disc 64 and strike the SCR 12. Such illumination of the SCR 12 causes the SCR 12 to become conductive which ultimately results in the reduction of the current in coil winding 18 to a value of zero with the consequent collapse of the previously established field about the windin g 18. Such reduction of the primary Winding 18 current causes a voltage increase in the secondary winding 20 and a sparking event at the related spark plug 28 through, of course, conductor 56 and rotor 22.

The manner in which such current reduction in the coil primary winding 13 is accomplished is generally as follows. As a consequence of the SCR 12 becoming conductive a portion of the transistor base 1% current is shunted through the SCR 12. The reduction in the current fiow through base ltltl results immediately in a substantial reduction in the current flow through the transistor emittercollector circuit, winding Stl and primary winding 18 of coil 16. The reduction in current flow through winding 59 causes the filed previously established thereabout to begin to collapse which in turn causes a voltage to be induced in coil 98 of the transistor base circuit. The voltage induced in coil 98 is in a direction tending to reverse bias the transistor 14 or, in other words, cause the base 10G to become relatively more positive. The base thusly becoming relatively more positive causes a further reduction in current flow through the transistor emitter 42-base ltltl circuit which, in turn, causes a further reduction in the current flow through coil 50. This action continues to repeat itself thereby causing the current flow through the emitter-base circuit, the current flow through coil 50 and the current flow through the primary winding 18 of coil 16 to be terminated.

The collapse of the field about winding 50 causes the induced voltage at base 1% to change from negative to a substantially positive value. After the positive voltage at base 100 attains some maximum value, the voltage across winding 98 starts to decay causing the induced positive voltage at base 1% to reduce in value so as to approach zero voltage and, further, once again become negative. During the period that the transistor base 100 is at a positive voltage and during the period that the induced voltage across winding 98 is decaying the silicon controlled rectifier 12 is still in a conductive state even though disc 64 has been rotated to a position whereat light emanating from source 68 is unable to impinge upon the SCR 12. The continued conduction of a light-triggered SCR even after removal of the light is an inherent characteristic of an SCR. Accordingly, the invention, in order to enable the use of an SCR provides means for positively causing the conducting SCR to become non-conductive in timed relationship to engine operation.

Once the induced voltage across winding 98 has completely decayed and base 100 has again become negative with respect to emitter 42, current flow is again established through the emitter-base circuit and the emittercollector circuit thereby producing current flow through winding 50 and coil assembly 16. This flow of current causes a field build up about winding 50 which causes a second voltage to be induced in winding 98 which voltage is in the direction of forward bias of the transistor or, in other words, in a direction which is opposite to that of the first voltage which was induced in Winding 98. This negative voltage pulse is then directed through conductor 96 against the SCR 12, as by gate 90 and the SCR 12 cathode 71 connected to conductor 72, thereby reducing the current through the cathode 71 to a level below that required to maintain conduction of the SCR 12. The SCR being turned ofi and non-conductive the current fiow through the emitter-base circuit is increased to design limits causing a relatively steady maximum current flow through the primary winding 18 of coil assembly 16. The SCR is, of course, again in condition for illumination in order to achieve the next sparking event at the next spark plug 28.

FIGURES 2 through 7 graphically illustrate the operating characteristics of the invention as described above. For example, in FIGURE 2 the current flow, in amperes, through the primary winding 18 of coil assembly 16 is plotted against time, with the units of current establishing the ordinate axis of the graph and the units of time comprising the axis of abscissas. An inspection of FIG- URE 2 discloses that when conduction through the emitter-collector circuit of transistor 14 is terminated, the current through primary coil 18 decreases from the substantially constant value represented at point 106 to zero as shown by point 108. The current value remains at zero for a relatively short length of time represented by point 110 at which time conduction through the emitter-collector circuit is again established causing 'a current in- .crease from zero, at point 110, to the designed maximum at point 112. Slight oscillations as indicated generally at 114 may precede the current again being stabilized at the maximum design value as indicated generally at 116.

FIGURE 3 is directly related to FIGURE 2. That is, the graph of FIGURE 3 illustrates a curve determined by plotting the voltage across primary coil 18 against time, starting at the same instant as that employed for determining the curve of FIGURE 2. In FIGURE 3 the units of voltage are measured along the ordinate axis while the units of time are measured along the axis of abscissas.

In comparing FIGURES 2 and 3 it can be seen that as current goes from a maximum value to zero that the voltage rises from a value of zero at point 118 to a maximum at point 120. Further, the spark duration which is from aprroximately points 129 to 122 is substantially coincident in terms of time with point 110 of FIGURE 2. Following the sparking event, a small oscillation is indicated generally at 124 may occur before the voltage again assumes a value of substantially zero.

FIGURE 4 graphically illustrates the voltage across the primary winding 56 while FIGURE 5 illustrates the voltage across winding 98. In each figure the units of voltage are measured along the ordinate axis while units of time are plotted along the abscissa. It should be noted that for purposes of clarity and illustration the time scales of both FIGURES 4 and 5, although identical to each other, are expanded with respect to FIGURES 2, 3, 6 and 7 which are, in turn, equal to each other. For purposes of reference, the graphs of FIGURES 4 and 5 are constructed as to have five graduat-ions of time equal to one graduation of time in FIGURES 2, 3, 6 and 7.

With reference to FIGURES 2 and 4 it can be seen that as current changes from point 106 to Zero at point 168 that the voltage increases from substantially zero at 128 of FIGURE 4 to a peak at 130. Subsequently, degeneration of the voltage occurs until it reaches a value of zero as indicated generally at 132. The time interval of from point 130 to point 132 is substantially equal and coincident with the interval between points 108 and 110 of FIGURE 2. The subsequent increase in current from point 110 to a maximum value at point 112 causes the voltage curve of FIGURE 4 to become negative and attain a negative peak as at 134 which, in terms of time, would be substantially coincident with or approaching point 112. Subsequent degeneration causes the voltage to again assume a value of substantially zero as indicated generally at 136. In comparing the curves of FIGURES 4 and 5 it can be seen that FIGURE 5 is an amplification of the curve in FIGURE 4. Accordingly, the respective points of similarity are identified with like primed reference numbers. It should be noted that the portion'of the voltage curve in FIGURE 5 described generally by points 128, 134) and 132 maintains transistor 14 in a non-conducting state (thereby establishing the time period between points 108 and 110 of FIGURE 2) and that the portion of the curve defined generally by points 132 (at a value of substantially zero) and 134' illustrates an increased oppositely directed voltage which causes the SCR 12 to become non-conductive. This is achieved because the negative voltage described by points 132 and 134' reduces the current flow through the SCR 12 below that level required to maintain the SCR 12 in a conductive state.

The invention provides a secondary feature which is of substantial benefit. That is, as described, it is apparent that during normal vehicle driving conditions a sparking event is cause for each required ignition event. However, at relatively slow engine speeds as, for example, during cranking or idling of the engine it is of material benefit to provide multiple sparking events for each required ignition event. This is especially beneficial in situations where engine cranking takes place in cold ambient temperatures.

Such multiple sparking events during relatively low engine speeds and engine cranking can be accomplished with this invention by selective sizing of the apertures 66 of disc 64 and proper placement of the shutter arrangement, lamp 63 and SCR 12.

That is, as long as the SCR is illuminated by lamp 68 the cycle of events leading to the sparking event will immediatelp repeat itself causing a second sparking event. Since the time required to complete one sparking event can be made to be substantially less than the time required for the beam of light 67 to impinge and traverse SCR 12 (remembering that the shutter or disc 64 is rotated in accordance with engine speed) it is then possible to cause multiple sparking events for each required ignition event.

This is illustrated, for example, by FIGURES 6 and 7 (respectively illustrating the voltage across coils 50 and 98) compared in terms of time to FIGURES 2 and 3. In view of the above description it becomes obvious that approximately three times the number of sparking events for each ignition event are occurring in the ignition system operating under a condition depicted by FIGURES 6 and 7 than one operating under a condition depicted by FIGURES 2 and 3. (Merely for reference in terms of voltage values, the reference numbers of FIGURES 4 and 5 are respectively employed in FIGURES 6 and 7.)

In one sucessful embodiment of the invention the circuit constants were as follows:

Transistor 14 2N1556 Silicon controlled rectifier (SCR) 12 1 L9AX3 Zener diode 102 1N3000 Diodes 84, 86, 88 1N4001 Coil assembly 16, turns ratio of primary to secondary 11350 1 General Electric Co.

Source of electrical potential 10 volts Norninally 12.0 Source of radiant energy (lamp 63) (2) General Electric Co. #253, 01' 'I'ung-Sol C0. #D521OGF.

As those skilled in the art know, the silicon controlled rectifier is sensitive to infra-red radiation. Therefore, it is not necessary that only such sources of radiant energy be employed which emit visible light. It should, of course, be apparent to those skilled in the art that such sources of radiant energy 68 can be employed which emit radiation having a wave length substantially only in that range of the spectrum defined as infra-red.

Accordingly, it should be specifically noted that any reference made herein and in the claims to a lamp, source of light, or bulb is intended to indicate any suitable source of radiant energy. Also, any reference made herein and in the claims to, for example, a bam of light, light, or light-energy is intended to mean such radiation or radiation energy as is necessary to achieve triggering of the semiconductor device 12.

It has also been discovered that under certain operating conditions Which occurred at or near the near of a sparking event that a reverse voltage Was induced into the primary Winding 18 of the coil assembly 16 which was of a magnitude sutficient to cause a proportionately large decrease in primary current. Such a decrease in current was also experienced by the coil or winding 50 which in-turn through core 106' and winding 9S caused the transistor 14 to switch off and become non-conductive. Once such action was initiated, oscillations of the entire ignition circuit could occur in synchronization with the natural frequency of the ignition coil secondary winding 20 as reflected into the primary winding 18.

Accordingly, in order to prevent such action from occurring, means are provided for compensating for the momentary decrease in current in winding 50 which, as previously stated, could occur due to the reverse voltage in the coil primary winding 18. It has been found that a coil or Winding 138 connected across conductors 46 and 62 would provide the desired compensation. The polarity of winding 138 is such that a coil primary 13 voltage which is negative at the grounded coil terminal 58 will force a current fiow in coil 138 which energies core 106'. The energizing ampere-turns from coil 133 are sutlicient to overcome and compensate for the input to the core 106 of the deenergizing ampere-turns from winding 50 and prevent the referred to oscillation of the entire ignition circuit.

A further advantage can be gained by the use of a resistor 1d0. The resistor 140, connected serially with coil 138 performs dual functions; that is, during that period of operation in which coil 138 is functioning as a compensating means, resistor 140 serves to limit the current flow through the coil 138 to the desired value and during other periods of operation it serves as a load resistor for coil 50. Accordingly, resistor 140 can then be considered as a calibrating means for tailoring the operating characteristics of the windings 50, 9S and 138.

In another successful embodiment of the invention the circuit included the following circuit constants in addition to those circuit constants previously set forth:

Resistor 140 ohms 200 Coil 138 turns 100 It should be apparent that the various values of the components, as disclosed herein, are presented merely as examples and are not intended to in anyway limit the scope of the invention.

The transistor 14 disclosed is of the P-N-P type; however, in view of the preceding description, it should be apparent to those skilled in the art that the invention can be practiced equally well by employing an N-P-N transistor since such alternative use merely requires appropriate reversal of polarities.

In view of the above, it should be appreciated that the invention as disclosed will maintain the selected spark timing indefinitely because the sparking event is lighttriggered therefore eliminating all wear problems from the triggering mechanism. Another important advantage of the invention, for example, over a mechanical breaker contact triggered power transistor ignition system, is that the triggering signal directed to the power transistor, according to the invention, is of a substantially consistent value regardless of engine speed. This same advantage also exists over the contactless pulsor type triggering mechanism of the prior art.

Although only a preferred embodiment of the invention has been disclosed and described, it is apparent that other embodiments and modifications of the invention are possible within the scope of the appended claims.

I claim:

1. An ignition system for an internal combustion engine having a spark discharge device, comprising a source of electrical potential, an ignition coil assembly having a primary winding and a secondary winding, means connecting said secondary winding with said spark discharge device, a transistor having emitter, base and collector electrodes, means connecting said emitter and collector electrodes in circuit between said source of electrical potential and said primary winding of said coil assembly, means normally maintaining said transistor in a conductive state so as to permit a charging current flow to said coil assembly primary winding, means including a lighttriggered silicon controlled rectifier device in shunt relationship to a circuit containing said emitter and base electrodes, and means operatve in timed relationship to Operation of said engine for directing a beam of light against said silicon controlled rectifier device in order to cause said silicon controlled rectifier device to become conductive thereby diminishing the flow of current from said source through said emitter-collector circuit by shunting at least a portion of such current flow available from said source around said emitter-base circuit and thereby causing a sparking event at said spark discharge device.

2. An ignition system 'for an internal combustion engine having a spark discharge device, comprising a source of electrical potential, an ignition coil assembly, means connecting said coil assembly to said spark discharge device, transistor means having emitter and collector electrodes connected in series circuit between said source and said ignition coil assembly, said transistor means being normally electrically biased so as to be conductive there by completing the circuit between said source and said coil assembly, a light-triggered semiconductor device connected in parallel relationship with said transistor means to said source of electrical potential, said semiconductor device being effective upon becoming conductive to cornplete a shunt circuit about said transistor means for causing said transistor means to become non-conductive in order to have said coil assembly discharge through said spark discharge device thereby causing a sparking event, means operative in timed relationship to engine operation for directing a beam of light against said light-triggered semi-conductor device, and signal means sensitive to the inductive voltage generated at initiation of said sparking event for applying a signal voltage to a base electrode of said transistor means for maintaining said transistor means in a state of non-conduction for a desired period of time.

3. An ignition system for an internal combustion engine having a spark discharge device, comprising a source of electrical potential, an ignition coil assembly, means connecting said coil assembly to said spark discharge device, transistor means having emitter and collector electrodes connected in series circuit between said source and said ignition coil assembly, said transistor means being normally electrically biased into conduction thereby completing the circuit between said source and said coil assembly, a light-triggered silicon controlled rectifier device connected in parallel relationship with said transistor means to said source of electrical potential, said rectifier device being effective upon becoming conductive to complete a shunt circuit about said transistor thereby substantially reducing the degree to which said transistor means is biased into conduction and permitting said transistor means to become non-conductive in order to have said coil assembly discharge through said spark discharge device causing the occurrence of a sparking event, means operative in timed relationship to engine operation for directing a beam of light against said light-triggered silicon controlled rectifier device for causing said rectifier device to become conductive, and signal means sensitive to the initiation of said sparking event for applying a signal voltage to a base electrode of said transistor means for maintaining said transistor in a state of non-conduction for a desired period of time and said signal means also being sensitive to the termination of said sparking event for applying a second signal voltage to said rectifier device for causing said rectifier device to become non-conductive.

4. An ignition system for an internal combustion engine having a spark discharge device, comprising a source of electrical potential, an ignition coil assembly, means connecting said coil assembly to said spark discharge device, transistor means having emitter and collector electrodes connected in series circuit between said source and said ignition coil assembly, said transistor means being normally electrically biased into conduction thereby completing the circuit between said source and said coil assembly and causing a current flow therethrough in a first direction, a light-triggered silicon controlled rectifier device connected in parallel relationship with said transistor means to said source of electrical potential, said rectifier device being effective upon becoming conductive to complete a shunt circuit about said transistor thereby substantially reducing the degree to which said transistor means is biased into conduction and permitting said transistor means to become non-conductive in order to have said coil assembly discharge through said spark discharge device causing the occurrence of a sparking event, means operative in timed relationship to engine operation for directing a beam of light against said light-triggered silicon controlled rectifier device for causing said rectifier device to become conductive, inductive coil means sensitive to the initiation of said sparking event for applying a signal voltage to a base electrode of said transistor means for maintaining said transistor in a state of non-conduction for a desired period of time, said inductive coil means also being sensitive to the termination of said sparking event for applying a second signal voltage to said rectifier device for causing said rectifier device to become non-conductive, and compensating coil means for overcoming current flows which are in a direction opposite to said first direction and induced into said series circuit between said coil assembly and said transistor means by said coil assembly near said termination of said sparking event.

5. An ignition system for internal combustion engine having a spark discharge device, comprising a source of electrical potential; a transistor having emitter, collector and base electrodes; first conductor means connecting one terminal of said source to said emitter electrode, said first conductor means including serially connected first manually positioned switch means for opening and closing the circuit through said first conductor means, and first and second resistance means; second manually positioned switch means for shunting said first resistance means during periods of engine cranking; an ignition coil assembly comprising a primary winding and a secondary winding; means for providing an electrical connection between said secondary winding and said spark discharge device; second conductor means connecting one terminal of said coil assembly to said collector electrode; said second con ductor means including serially connected first coil means and third resistance means; third conductor means connecting an other terminal of said coil assembly to an other terminal of said source; a Zener diode electrically connected to said first conductor means at a point generally between said emitter electrode and said second resistance means and electrically connected to said second conductor means at a point generally between said first coil means and said third resistance means; fourth conductor means connected to said first conductor means at a point generally between said first and second resistance means and connected to said third conductor means generally between said other terminal of said source and said other terminal of said coil assembly; said fourth conductor means including serially connected fourth resistance means and a light-triggered silicon controlled rectifier having a gate electrode; fifth conductor means electrically connected to said base electrode and to said fourth conductor means at a point generally between said rectifier and said fourth resistance means, said fifth conductor means including a second coil means placed in close proximity to said first coil means; a fifth resistance means electrically connected in series between said gate electrode and said fourth conductor means at a point generally between said rectifier and said fourth resistance means; sixth conductor means connected at one end to said third conductor means at a point generally between said other ter' minal of said source and said point of connection with said fourth conductor means; seventh conductor means connected at one end to said third conductor means at a point generally between said points of connection with said fourth conductor means and said sixth conductor means; the other ends of said sixth and seventh conductor means being electrically connected together so as to form parallel branch conductors; said sixth conductor means ineluding diode means between said one end and said other end of said sixth conductor means; lamp means serially connected in said seventh conductor means; eighth conductor means, including sixth serially connected resistance, electrically connected at one end to said sixth and seventh conductor means and having an otther end electrically conected to said fourth conductor means at a point generally between the point of connection of said fourth conductor means and said first conductor means and said rectifier; third coil means electrically connected at one end to said second conductor means at a point generally between said first coil means and said third resistance means, said third coil means also being connected at its other end to seventh resistance means which has another end electrically connected to said third conductor means at a point generally between said other terminal of said coil assembly and the point of connection between said third conductor means and said fourth conductor means; and shutter means operated in timed relationship to the operation of said engine for intermittently causing a beam of light from said lamp means to strike said rectifier.

6. An ignition system for an internal combustion engine having a spark discharge device, comprising a source of electrical potential; a transistor having emitter, collector and base electrodes: first conductor means connecting one terminal of said source to said emitter electrode, said first conductor means including serially connected first manually positioned switch means for opening and closing the circuit through said first conductor means and first resistance means serially connected there: in; an ignition coil assembly comprising a primary wind ing and a secondary winding; means for providing an electrical connection between said secondary winding and said spark discharge device; second conductor means connecting one terminal of said coil assembly to said. collector electrode, said second conductor means including serially connected first coil means and second resistance means; third conductor means connecting an other terminal of said oil assembly to an other terminal of said source; a Zener diode electrically connected to said first conductor means at a point generally between said emitter electrode and said first resistance means and electrically connected to said second conductor means at a point generally between said first coil means and said second resistance means; fourth conductor means connected to said first conductor means at a point generally between said first resistance means and said emitter electrode and connected to said third conductor means generally between said other terminal of said source and said other terminal of said coil assembly, said fourth conductor means including serially connected third resistance means and a light-triggered silicon controlled rectifier having a gate electrode; fifth conductor means electrically connected to said base electrode and to said fourth conductor means at a point generally between said rectifier and said third resistance means, said fifth conductor means including a second coil means placed in close proximity to said first coil means; a fourth resistance means electrically connected in series between said gate electrode and said fourth conductor means at a point generally between said rectifier and said third resistance means; sixth conductor means connected at one end to said third conductor means at a point generally between said other terminal of said source and said point of connection with said fourth conductor means; seventh conductor means connected at one end to said third conductor means at a point generally between said points of connection with said fourth conductor means and said sixth conductor means; the other ends of said sixth and seventh conductor means being electrically connected together so as to form parallel branch conductors; said sixth conductor means including diode means between said one end and said other end of said sixth conductor means; lamp means serially connected in said seventh conductor means; eighth conductor means, including fifth serially connected resistance electrically connected at one end to said sixth and seventh conductor means and having an other end electrically connected to said fourth conductor means at a point generally between the point of connection of said fourth conductor means and said first conductor means and said rectifier; third coil means electrically connected at one end to said second conductor means at a point generally between said first coil means and said second resistance means, said third coil means also being connected at its other end to a sixth resistance means which has an other end electrically connected to said third conductor means at a point generally between said other terminal of said coil assembly and the point of connection between said third conductor means and said fourth conductor means; and shutter means operated in timed relationship to the operation of said engine for intermittently causing a beam of light from said lamp means to strike said rectifier.

7. An ignition system for an internal combustion engine having a spark discharge device, comprising a source of electrical potential; a transistor having emitter, collector and base electrodes; first conductor means connecting one terminal of said source to said emitter electrode; an ignition coil assembly comprising a primary winding and a secondary winding; means for providing an electrical connection between said secondary winding and said spark discharge device; second conductor means connecting one terminal of said coil assembly to said collector electrode; third conductor means connecting an other terminal of said coil assembly to an other terminal of said source; fourth conductor means having its opposite ends respectively connected to said first conductor means and said third conductor means, said fourth conductor means including serially connected therein a lighttriggered silicon controlled rectifier; fifth conductor means electrically connected to said base electrode and to said fourth conductor means; and a signal transformer having primary and secondary coils, said transformer being arranged so as to have said primary coil in series circuit with said second conductor means and so as to have said secondary coil in series circuit with said fifth conductor means, said primary coil being effective to produce a voltage signal as an indicia of the change in current fiow therethrough and said secondary coil being effective to amplify said voltage signal and apply such an amplified voltage signal to said base electrode by virtue of its series circuit connection with said fifth conductor means in order to employ said amplified voltage signal for reducing the current flow through the transistor emitter and collector electrodes.

8. An ignition system for an internal combustion engine having a spark discharge device, comprising a source of electrical potential; a transistor having emitter, collector and base electrodes; first conductor means connecting one terminal of said source to said emitter electrode; an ignition coil assembly comprising a primary winding and a, secondary winding; means for providing an electrical connection between said secondary winding and said spark discharge device; second conductor means connecting one terminal of said coil assembly to said collector electrode; third conductor means connecting an other terminal of said coil assembly to an other terminal of said source; fourth conductor means having its opposite ends respectively connected to said first conductor means and said third conductor means, said fourth conductor means including serially connected therein a lighttriggered silicon controlled rectifier; fifth conductor means electrically connected to said base electrode and to said fourth conductor means at a point in said fourth conductor means between said rectifier and said third conductor mean-s; a source of light energy; shutter means operated in timed relationship to engine operation for intermittently causing a beam of light from said source of light energy to strike said rectifier; and a signal transformer having primary and secondary coils, said transformer being arranged so as to have said primary coil in series circuit with said second conductor means and so as to have said secondary coil in series circuit with said fifth conductor means, said primary coil being effective to produce a voltage signal as an indication of the change in current flow therethrough, said secondary coil being effective to amplify said voltage signal and apply such an amplified voltage signal to said base electrode by virtue of its connection with said fifth conductor means in order to employ said amplified voltage signal for reducing the current flow through the transistor emitter and collector electrodes and apply said amplified voltage signal to said rectifier by means of said fourth conductor to terminate conduction through said rectifier.

9. An ignition system for an internal combustion engine having a spark discharge device, comprising a source of electrical potential; a transistor having emitter, collector and base electrodes; first conductor means connecting one terminal of said source to said emitter electrode, an ignition coil asembly comprising a primary winding and a secondary winding; means for providing an electrical connection between said secondary winding and said spark discharge device; second conductor means connecting one terminal of said coil assembly to said collector electrode; third conductor means connecting an other terminal of said coil assembly to an other terminal of said source; fourth conductor means connected to said first conductor means and said third conductor means, said fourth conductor means including serially connected therein a light-triggered silicon controlled rectifier; fifth conductor means electrically connected to said base electrode and to said fourth conductor means; a source of light energy; shutter means operated in timed relationship to engine operation for intermittently causing a beam of 13 light from said source of light energy to strike said rectifier in order to make said rectifier conductive; a signal transformer having primary and secondary coils, said transformer being arranged so as to have its primary coil in series circuit with said second conductor means and so as to have said secondary coil in series circuit with said lfifth conductor means, said primary coil being effective to produce a voltage signal as an indication of the change in current flow therethrough, said secondary coil being eifective to amplify said voltage signal and apply such an amplified voltage signal to said base electrode by virtue of its connection to said *fifth conductor means in order to employ said amplified voltage signal at times for maintaining said transistor in a non conductive state While at other times applying such an amplified voltage signal to said rectifier by virtue of its connection to said fifth and fourth conductors for causing said rectifier to become non-conductive; and current compensating means comprising an additional coil connected to said primary coil for opposing the creation of voltage signals by said primary coil which might arise in response to voltages i l developed in said ignition coil assembly after said coil assembly has discharged through said spark discharge device.

References Cited OTHER REFERENCES E. Keith Howell, Light-activated Switch Expands Uses of Silicon-Controlled Rectifiers. Appearing in r Electronics, vol. 37, No. 15; May 4, 1964, pp. 5361.

JOHN W. HUCKERT, Primary Examiner.

JAMES D. KALLAM, Examiner.

D. O. KRAFT, I. D. CRAIG, Assistant Examiners. 

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE HAVING A SPARK DISCHARGE DEVICE, COMPRISING A SOURCE OF ELECTRICAL POTENTIAL, AN IGNITION COIL ASSEMBLY HAVING A PRIMARY WINDING AND A SECONDARY WINDING, MEANS CONNECTING SAID SECONDARY WINDING WITH SAID SPARK DISCHARGE DEVICE, A TRANSISTOR HAVING EMITTER, BASE AND COLLECTOR ELECTRODES, MEANS CONNECTING SAID EMITTER AND COLLECTOR ELECTRODES IN CIRCUIT BETWEEN SAID SOURCE OF ELECTRICAL POTENTIAL AND SAID PRIMARY WINDING OF SAID COIL ASSEMBLY, MEANS NORMALLY MAINTAINING SAID TRANSISTOR IN A CONDUCTIVE STATE SO AS TO PERMIT A CHARGING CURRENT FLOW TO SAID COIL ASSEMBLY PRIMARY WINDING, MEANS INCLUDING A LIGHTTRIGGERED SILICON CONTROLLED RECTIFIER DEVICE IN SHUNT RELATIONSHIP TO A CIRCUIT CONTAINING SAID EMITTER AND BASE ELECTRODES, AND MEANS OPERATIVE IN TIMED RELATIONSHIP TO OPERATION OF SAID ENGINE FOR DIRECTING A BEAM OF LIGHT AGAINST SAID SILICON CONTROLLED RECTIFIER DEVICE IN ORDER TO CAUSE SAID SILICON CONTROLLED RECTIFIER DEVICE TO BECOME CONDUCTIVE THEREBY DIMINISHING THE FLOW OF CURRENT FROM SAID SOURCE THROUGH SAID EMITTER-COLLECTOR CIRCUIT BY SHUNTING AT LEAST A PORTION OF SUCH CURRENT FLOW AVAILABLE FROM SAID SOURCE AROUND SAID EMITTER-BASE CIRCUIT AND THEREBY CAUSING A SPARKING EVENT AT SAID SPARK DISCHARGE DEVICE. 